PROJECT SUMMARY/ABSTRACT Original Grant Celiac disease (CD) is an autoimmune disorder of the small intestine, afflicting about 1% of the world's population, for which there is no cure. Currently the only therapeutic option to avoid gastrointestinal-related symptoms and potentially long-term health consequences is the life-long strict adherence to a gluten-free diet (GFD). However, a majority of patients never fully recover. There is a huge unmet need for a therapeu- tic solution to be used as an adjunct to a GFD. There is a further unmet need for an effective and minimally- invasive tool to monitor small intestinal recovery in CD patients as an alternative to esophagogastroduo- denoscopy (EGD), which is invasive, costly and not generally recommended by clinicians for disease moni- toring. ImmunogenX is a clinical-stage therapeutic and diagnostic company focused on celiac disease (CD). Our lead product development is the orally administered enzyme product latiglutenase, which has shown evidence for histologic protection and symptom reduction in response to exposure to moderate amounts of dietary gluten. The mechanism of action is the proteolytic digestion along specific glutamine and proline bonds of digestively resistant gluten peptides in the stomach using a combination of two digestive enzymes. Our diagnostic product CypCel is based on a drug biomarker simvastatin (SV) that is highly metabolized in the small intestine and is present in blood at concentrations that are proportional to the extent of villous health. Latiglutenase, a two-enzyme natural product, has a strong scientific premise to justify further clinical testing. It has been shown in a variety of model stomach experiments to detoxify antigenic gluten proteins. Furthermore, there has been sufficient animal and human safety data to be registered as a dietary supple- ment. However, we would first like to obtain more scientific data to inform us on the most responsible and optimal path toward further development and product launch. Previous clinical trials have yielded encourag- ing but inconclusive information regarding its impact on improving mucosal health. We propose to the NCCIH a study to fill this gap in our scientific knowledge. In this application, we propose a human study consisting of a gluten-challenge for diagnosed CD pa- tients in remission. We will employ placebo and latiglutenase arms in a 1:1 ratio and will measure the bio- logical signatures for mucosal changes using biopsy readings of villous height to crypt depth ratio (Vh:Cd) and CypCel measurements (as a minimally-invasive indicator of mucosal health). The trial will be powered to a primary endpoint for biopsy Vh:Cd and secondary endpoint for SV level in serum and plasma samples collected at 5 time points after administration of SV. Our enrollment target based on adequate powering of the primary and secondary endpoints is 42 completed patients. We will also employ the recently validated Celiac Disease Symptom Diary patient reported outcome (CDSD? PRO) tool for CD symptoms in order to demonstrate an association between the change in the biological signature (Vh:Cd) and improvement in a clinical outcome (symptoms). We anticipate completing this enrollment at Mayo Clinic (Rochester, MN) where we have already initiated a CypCel trial. This work will provide vital scientific data to help justify fur- ther clinical testing. Supplemental Work We request supplemental funds to extend the trial into a third year. For several unanticipated reasons, the trial planning was more complicated and expensive to start, but is now showing healthy enrollment and operational success. We originally proposed this as a 2-year project with tight funding limits, but accepted that we would have to provide co-funding to meet the cost of a Phase 2 clinical trial. In hindsight we should have recognized that a third year would be needed. We seek a third year of funding to complete this very important and now operationally robust trial. 1